Free developer tools
Each tool answers one question about running projects on your own machine: which keys are missing from a .env file, whether a Procfile is valid, which command shows what holds a port, which ports to give a stack, and what MCP config a coding agent needs. They run in your browser, and nothing you enter is uploaded. Every tool page states the rules it applies, shows a worked example, and says what the tool cannot check.
All tools
- Free tool
Env file diff checker
Compare .env with .env.example in your browser. Find missing, extra, duplicate, empty, and malformed keys, then copy a block of the missing ones.
- Free tool
Port in use command generator
Get the exact commands to find which process uses a port and stop it on macOS, Linux, or Windows, with every flag explained and the safe order first.
- Free tool
Local dev port planner
List the services you run locally and get a port plan with no clashes. It flags privileged and ephemeral ports and gives .env, Procfile, and Compose snippets.
- Free tool
MCP config generator
Generate MCP server config for Claude Code, Cursor, Codex, VS Code, and more: file paths, exact JSON or TOML, add commands, and a snippet converter.
- Free tool
Procfile validator
Check a Procfile for invalid lines, repeated process types, a missing web process, and $PORT use. See what Heroku and Rig accept, then copy a clean version.
What each page contains
A tool page has the tool, a worked example, the rules the tool applies in plain language, its limits, and common mistakes. The example’s output is produced by the same code the tool runs, so the example cannot drift from what the tool does.
How the tools are checked
Claims about other projects come from their official documentation, and each source is recorded with the date it was checked. Claims about Rig come from Rig’s source code. Formats that vendors change, such as MCP client config, name the date they were last checked.
How the pages are kept current
Every page records the date of its last substantive update. A page that is still a draft is not published, and a published page that fails a quality check is held back. The background for each tool is in the topic hubs.
Frequently asked questions
Do these tools send what I paste anywhere?
No. Each tool runs in your browser and makes no network request for your input. Even so, avoid pasting production secrets into any web page. The env file diff checker needs only key names and whether a value is empty, so replace each real value with x, and leave empty values empty, before you paste.